As it is known, in a packet-switched network data are transmitted in discrete units of potentially variable length blocks called packets. Each packet contains not only data but also a header with control information. In a connectionless network the information transfer between users/terminals happens without establishing a logical connection or virtual circuit between those specific users/terminals.
Internet is the most used example of a connectionless packet-switched network which is IP-based. Particularly, an IP-based network employs TCP/IP (Transmission Control Protocol/Internet Protocol) model comprising the so called Internet protocol suite, according to which the communications on the network are described by a five-layers model comprising the following layers: Physical, Data Link, Network, Transport and Application.
Particularly, the Network layer is responsible for the source-to-destination delivery of a packet possibly across multiple networks and the Application or “Service” layer supports the end-user, software or human, in accessing the network resources. The layers of the TCP/IP model can be mapped on the ISO/OSI (International Standard Organization/open Systems Interconnection) seven-layers model.
An IP-based network follows a client-server strategy wherein an application program, the client, running on a local machine, requests a service from another application program, called server and running on a remote machine. Normally, an IP-based network is provided with different known devices such as, routers, switches etc., each operating at different layers of the TCP/IP protocol suite.
IP-based network employing proxies are known. A proxy is a program interposed between a client and a server, which offers a network service to allow clients to make indirect network connections to other network services, by using some protocols of the Application layer of the TCP/IP model (e.g., HTTP, FTP, SIP, etc.). The client sends to the proxy a request and the proxy may perform several actions on the request before routing it to the destination.
Cisco Systems, Inc. has proposed an Application Oriented Networking (AON) platform to be used in network employing TCP protocol. Cisco AON embeds a class of application intelligence into the network to meet the needs for multienterprise security, real time visibility, event-driven messaging, optimized delivery. In accordance with this technology, standard routers are enhanced with supervisor engine or route processor in order to transparently redirect application traffic to the Cisco AON module. AON service logic can then be applied to these messages, which are subsequently forwarded to the destination application.
Document U.S. Pat. No. 6,970,913 describes a method of load-balancing according to which a forwarding agent is implemented in a router of an IP-based network comprising clients, servers and service managers. This document discloses packets exchange between the enhanced routers and the service managers in order to perform load-balancing, i.e. distributing requests to different servers, with the goal of optimizing system performance. The Applicant observes that the service managers described by document U.S. Pat. No. 6,970,913 operate at the network layer of the protocol suite.
Document U.S. Pat. No. 6,912,570 describes a method for dynamically modifying a stateful inspection of data and discloses a router adapted to perform a stateful inspection of packets passing therethrough. As it is known, stateful inspection, also referred to as dynamic packet filtering, is a firewall architecture that works at the network layer. The above indicated document refers to a method that exploits such inspection to enable an enhanced use of Quality of Service (QoS) classification based upon the high level application of the data.